Mobility management state transition system and method for handling dark beam scenarios

ABSTRACT

A state transition diagram is presented for a user&#39;s access terminal for a satellite telecommunication system, showing the state of the access terminal&#39;s mobility management software layer, in response to various stimuli and conditions as the user enters into and out of various modes of operations, including deactivation, activation and illumination of a dark beam of a spot beam that is a shared resource.

[0001] This application claims benefit under 35 U.S.C. §119(e) fromprovisional patent application Serial No. 60/317,560, filed on Sept. 6,2001, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to cellular and satellitecommunications. More particularly, the invention relates to a method andsystem of sharing radio resources between at least one existing serviceprovider and a second existing or new service provider, to provide bothnew and existing services to their respective users.

BACKGROUND OF THE INVENTION

[0003] Great advances in the field of wireless communications have beenmade over the past ten to twenty years, and continue to be made. Theseadvances both improve the quality of communication, e.g., the clarityand reliability of communication, and improve the geographic coverage ofsuch wireless communications. As industry strives to provide a wirelesscommunications capability that covers the entire globe, factors such aseconomic viability dictate that space-based transceivers be employed tocompliment ground infrastructure. Ground infrastructure remainstechnologically advantageous and economically preferable in identifiedpopulation centers where a great deal of bandwidth is required in arelatively small area. However, satellites can provide universalcoverage economically extending coverage over less populated areas.Thus, two types of wireless communication, i.e., ground infrastructurecellular, and space-based satellite systems have emerged. One of themost ubiquitous terrestrial cellular systems is the Global System forMobile Communications (GSM). Geo Mobile Radio (GMR-1) is an example ofsystems which are extensions of GSM to the mobile satellitecommunication system venue.

[0004] In both types wireless communication systems, there are physicalchannels and logical channels. A physical channel in GSM or GMR-1 is acontinuous allocation of resources including both a frequency and a timecomponent. The frequency is given by an absolute radio frequency channelnumber (ARFCN) allocation, and the time component is given by theallocated time slot(s) within a frame. Logical channels are mapped tophysical channels. Logical air interface channels of interest include:broadcast control channel (BCCH) 5 (from network to a user accessterminal or forward direction); random access channel (RACH) 19 (fromuser access terminal to network or return direction); and access grantchannel (AGCH) 21 (forward direction). The network uses logical channelsto convey signaling and control message. For example, system informationmessages are conveyed on the BCCH 5, channel request messages areconveyed on the RACH 19 and immediate assignment reject and immediateassignment messages are conveyed on the AGCH 21. Messages containinformation elements and information elements can have many differentvalues.

[0005]FIG. 1 illustrates a block diagram of a satellite communicationsystem according to the prior art. A satellite communications network,such as a geo-synchronous earth orbit mobile communications network,comprises at least one geo-synchronous earth orbit satellite 6, aground-based resource manager (RM) 16 and spacecraft operations center(SOC), associated with satellite 6, at least one ground-based existinggateway station (EGW) 8, and at least one user access terminal 20, whichis typically a hand-held or vehicle mounted mobile telephone. Satellite6 enables access terminal 20 to communicate with other access terminals20 or with other telephones in a terrestrial network (for example, apublic switched telephone network or PSTN), via the gateway stations. RM16 provides system-wide resource management, and the SOC controlson-orbit satellite operations for its respective satellite 6. A systemmay comprise one or more satellites 6.

[0006] In a terrestrial cellular system an antenna's coverage area (bothreceive and transmit) is known as a cell. The equivalent concept in amobile satellite system is a spot beam. The spot beam is defined as thecoverage area of a satellite antenna or antenna subsystem, which mayconsist of a phased an-ay or a multiplicity of antenna elements with orwithout a reflector. The typical mobile satellite may have hundreds ofspot beams. A “cell” or “spot beam” is defined to exist independent ofwhether or not it is actually radiating or receiving energy at the time.Thus, we can define an illuminated spot beam as a beam into which energyis actually being radiated by the antenna and a dark spot beam as a beamin which the satellite's antenna is not radiating any energy or asignal. More specifically, the transmission of BCCH 5 into the cell orspot beam is required.

[0007] The spot beam in FIG. 1 shall be referred to as spot beam 10.BCCH 5 contains the system information necessary for access terminal 20to receive so that it can be aware of the cell or spot beam's 10existence. In GSM cellular technology specifications an access terminalis referred to as a “mobile station” (MS). In the GMR-1 mobile satellitespecifications an access terminal is referred to as a “mobile earthstation” (MES). For generality, the term “access terminal” 20 will beused in this document

[0008] The system information messages broadcast by the network on theBCCH 5 contain the information necessary for access terminal 20 (asshown in FIG. 1) to determine where the RACH 19 and AGCH 21 channels are(timeslots and ARFCNs) and any rules governing the use of the RACH 19channel by access terminal 20. In GSM and GMR-1, RACH 19 channels andAGCH 21 channels are paired so that an access terminal's channel requestmessage on a specific RACH 19 will always be responded to by animmediate assignment or immediate assignment reject message from thenetwork on the specific paired AGCH 21. The system information messagesbroadcast on the BCCH 5 channel also contain information elements whichdescribe the service provider bearer services which are offered toaccess terminal 20 within the spot beam or cell. A GMR-1 BCCH 5 alsocontains a concurrent BCCH list, which is a list of BCCHs 5 beingbroadcast into the same spot beam 10 by the network and their servicesand service providers. Except for the concurrent BCCH list, all of thisinformation or its equivalent exists in GSM. All of the informationwhich the terminal needs to know in order to operate within the systemis contained in the system information messages.

[0009] GMR-1 05.005 and GSM 05.05 partition the radio frequency spectrumavailable to the air interface into radio frequency channels, anddefines an ARFCN for each channel. Each spot beam in GMR-1 (or cell inGSM) is allocated a subset of these channels. These channels process aredefined as the beam allocation. One radio frequency channel of the beamallocation is used by the network to broadcast the BCCH and is known asthe BCCH carrier.

[0010] GSM and GMR-1 use time division multiplexing (TDMA). Time ispartitioned into TDMA frames and timeslots as defined in GMR-1 05.002and GSM 05.02. The transmissions within these timeslots are known asbursts. A burst is a single unit of transmission on the radio pathdefined in terms of center frequency (or ARFCN), bandwidth, powerprofile, and duration (in numbers of contiguous timeslots).

[0011] Logical channels are mapped to physical channels by a set ofmultiplexing rules. They can be statically or dynamically mapped tophysical channels. These rules are defined in GSM 05.02 for GSM andGMR-1 05.002 for GMR-1.

[0012] At present, the typical mobile communications satellites arenon-processing satellites or bent-pipe satellites. That means that allphysical bursts are transmitted or originated by a ground-basedtransmitter, either an access terminal 20, EGW 8 or new gateway (NGW)12, and these are received and retransmitted by the satellite. Satellite6 does not initiate transmission or originate physical bursts.Typically, there is a radio frequency spectrum allocated to the linkbetween access terminal 20 and satellite 6 and another radio frequencyspectrum allocated to the feeder link between satellite 6 and EGW 8. IfEGW 8 transmits a burst on the feeder link, satellite 6 receives theburst and performs a frequency translation from the feeder linkfrequency to an appropriately allocated ARFCN and retransmits the burston the forward link ARFCN into spot beam 10. If no feeder link burst ispresent satellite 6 has no signal to retransmit. Also, if accessterminal 20 transmits a burst on an appropriately allocated ARFCN returnlink, satellite 6 receives the burst and performs a frequencytranslation to the appropriately allocated feeder link frequency andretransmits the burst from access terminal's 20 signal to EGW 8.

[0013] When an access terminal 20 is turned on or powered up it searchesfor a BCCH 5 broadcast in a spot beam 10. Since there can be hundreds ofspot beams 10, the access terminal 20 must perform a task called spotbeam selection. Spot beam selection in GMR-1 is described in GMR-1specifications 03.022 and 05.008 and in U.S. Pat. No. 6,233,451, “SPOTBEAM SELECTION IN A MOBILE SATELLITE COMMUNICATION SYSTEM”, (the entirecontents of which are expressly incorporated herein by reference). Spotbeam selection is the selecting of a BCCH carrier to “camp-on”, whichcombines comparison and selection based on received signal strengths ofBCCH carriers with a comparison and selection based on service provideror PLMN identity. Briefly, In GSM, access terminal 20 measures the powerin all the BCCH carriers and selects all the ones with received signalstrengths greater than some criteria and creates a rank-ordered list.The access terminal 20 then reads the system information broadcast onthe BCCHs 5 of the BCCH carriers in the rank-ordered list and selectsthe one, which has a preferred service provider or PLMN. This is oftennot the closest cell or the strongest signal.

[0014] In GMR-1, in order to conserve satellite power and accessterminal 20 power during communications, it is important that the accessterminal 20 always select the correct spot beam. To assist the accessterminal 20, two lists are broadcast in the system information of eachBCCH 5, the neighbor list and the concurrent BCCH list. The neighborlist is a list of BCCH carriers used in the adjoining spot beams 10. Theaccess terminal 20 makes measurements of these neighbors for signalstrength comparison. The concurrent BCCH list is a list of all BCCHcarriers in the same spot beam. These may be from a different EGW 8 orNGW 12. The concurrent BCCH List includes the PLMN ID, which is theservice provider identity of the operator of the system broadcasting theconcurrent BCCH. The PLMN ID is referred to as the “public land mobilenetwork identifier” and it is composed of a mobile country code (MCC),and a mobile network code (MNC). The access terminal 20 avoidsmeasurement comparison of concurrent BCCH carriers to make a spot beamselection, however once the access terminal 20 selects a spot beam 10,it compares PLMN identities of each BCCH 5 on the concurrent list and“camps-on” the BCCH carrier with a preferred PLMN.

[0015] As a further innovation of GMR-1, the access terminal 20 hasincorporated a Global Positioning System (GPS) receiver. The systeminformation message in the BCCH 5 also contains the latitude andlongitude of the spot beam 10 center. Access terminal 20 may optionallycompare its GPS position to the spot beam center position to accuratelydetermine the correct spot beam. Since access terminal 20 is required toreport this position in the channel request message, the network mayoptionally redirect the access terminal 20 to a different spot beam 10based on a comparison of the reported access terminal 20 position andthe coverage area map of all spot beams 10.

[0016] In order to support ubiquitous service throughout the satellite'scoverage area, a gateway (EGW 8 or NGW 12) must broadcast a BCCH (BCCH 5and BCCH 5′, respectively) into every existing spot beam 10. This meansthat the RM 16 must allocate at least one BCCH 5 carrier for each spotbeam 10 for use by the gateway RM 16. Further, satellite power must beallocated for each spot beam 10 to be illuminated by the gateway with aBCCH 5 (or BCCH 5′) transmission.

[0017] Having selected a spot beam 10 and a BCCH carrier, the accessterminal 20 must transmit a channel request message on the RACH 19 (orRACH 19) channel to request a traffic channel for communication of userdata and/or signaling. Prior to transmitting this message, however, theaccess terminal 20 must make one more check. It must read thecell-bar-access bit in the system information to determine if accessterminals are barred from attempting access to the cell or spot beam. Ifthis bit is ‘1’ access is barred and if the bit is ‘0’ access ispermitted. In the case assess is permitted, the access terminal 20 wouldrequest a channel with the establishment cause “to register”. Thedefinition of the cell bar access bit is shown in Table 1. If the usersubsequently wanted to make a phone call, the access terminal 20 wouldrequest a channel for that purpose with establishment cause “tooriginate a call”. Alternatively, someone in the PSTN might call theuser, in which case, having registered with the network. the networkknows the location, cell or spot beam and can page the access terminal.Upon receiving a page, the access terminal 20 transmits a channelrequest message with establishment cause “responding to a page.” Otherestablishment causes exist. TABLE I Cell Bar Access Any Service 1 Barred0 Not Barred

[0018] In the prior art of GSM and other cellular and mobile satellitesystems, the channel request message typically only contains a randomreference and an establishment cause. A random reference is a uniquerandom number generated by access terminal 20 and passed to the gatewaywithin the RACH message, and which uniquely identifies that accessterminal 20. It is used by the gateway to address access terminal 20when sending the immediate assignment or immediate assignment rejectmessage to access terminal 20 on the AGCH 21 (or AGCH 21′). This is usedin the event of contention, between a first and second (or any numberof) access terminals 20. As we have seen, the establishment cause tellsthe gateway the reason the access terminal 20 is requesting a channel(i.e., the reason to “establish” a channel). An innovation, introducedin the prior art of GMR-1, is for the channel request message to containmuch more detailed information about the establishment cause and therequesting access terminal 20. The GMR-1 channel request messagecontains, in addition to the establishment cause and random reference,the SP/HPLMN ID (Service Provider/Home Public Land Mobile Network), thecalled party number, the GPS-derived position of the access terminal 20and other information elements. The network reads all of theseinformation elements and determines the disposition of the channelrequest message from access terminal 20. Any of the values of theseinformation elements may trigger existing gateway (EGW) 8 to processaccess terminal's 20 request for access in a specific way, such assetting up a terminal-to-terminal call (described in GMR-1 specification03.096) or optimally routing the call to another EGW 8 (described inGMR-1 specification 03.097) or rejecting the call based on geographiclocation, (described in GMR-1 specification 03.099) etc. None of theseservices are offered in GSM and there is no comparable specification.

[0019] U.S. Pat. No. 6,249,677, (the entire contents of which are hereinincorporated by reference), is entitled “Apparatus and Method forDelivering Key Information of a Channel Request Message From a UserTerminal to a Network” and discloses an apparatus and method, for usewith the satellite-based communications network, for improving thereliability and speed at which communication between a user terminal andthe network is established. The apparatus and method arranges data of achannel request message transmitted from a user terminal to a satellitein the satellite-based network to insure that the most critical data forestablishing communication between the user terminal and thesatellite-based network is received at the satellite during theappropriate receiving time frame window. The channel request messageincludes a first data group necessary for establishing a communicationlink for which information is transmitted between the apparatus and thenetwork, and a second data group including information for decreasingthe amount time necessary to establish the communication link. The firstdata group is positioned at the center of the Channel Request Message,with portions of the second data group at opposite ends of the ChannelRequest Message. The time at which the user terminal transmits theChannel Request Message is set based on a location of the apparatuswithin a spot beam, to take into account the appropriate propagationdelay time for the message to travel from the apparatus to the satellitein the network, thus assuring that at least the first data group of theChannel Request Message is received at the satellite during anappropriate receiving time frame window.

[0020]FIG. 2 illustrates a message flow diagram showing theestablishment of a communications channel between an access terminal andthe network according to the prior art. As discussed above, EGW 8continuously transmits BCCH 5 (step 202), which contains systeminformation messages. In step 204, access terminal 20 “camps on” BCCH 5,and retrieves the critical system information. Included in this systeminformation is the frequency identity of the RACH 19 channel whichaccess terminal 20 may use to communicate with EGW 8. For example,access terminal may transmit a channel request message to EGW 8 in orderto access existing services. Upon receiving the channel request messagefrom the access terminal 20 on the RACH 19 (step 206) the networkresponds with either an immediate assignment or an immediate assignmentreject message on the AGCH 21 (step 204). Communication on a trafficchannel may then begin, as shown in step 210.

[0021] As described, in order to offer wireless mobile service, anetwork or system must advertise its presence and capabilities viasystem information messages broadcast on the BCCH 5. This broadcastcosts resources to a service provider. These resources include spectrum,power as well as radio equipment. When there are two gateway stationsserving the same spot beam 10, each gateway stations must use an RFcarrier as the BCCH carrier and each gateway station must broadcast theBCCH 5 continuously, in order for the access terminal 20 to discover andread the system information on the BCCH 5 and access services (step 210)from the gateway. Both gateways must illuminate their BCCH carriers.

[0022] A new service provider or the existing service provider,launching a new service, is normally required to spend resources tobroadcast the system information associated with the new service. Inorder to support ubiquitous service in the entire coverage area of thesatellite system, by the prior art, the NGW 12 must broadcast a BCCH 5in every spot beam. This requires the allocation of at least one BCCHcarrier for every spot beam 10, an allocation of satellite power forevery spot beam 10, and the allocation of other required systemresources, such as transmitters sufficient to support the transmissionof a BCCH 5 in every spot beam 10 by NGW 12. Accordingly, a need arisesto allow an existing service provider, which is already providingubiquitous service, to support by proxy a second service provider and/ora new service. Such as capability offers the opportunity to save systemresources. However, a method is required, which minimizes the impact tothe existing proxy network, and at the same time requires nomodifications to the user access terminal 20 already using the proxynetwork for existing services, and minimal modifications to a new accessterminal 20 and existing gateway station equipment.

[0023]FIG. 3 illustrates a state transition diagram for a GSM/GPRSmobility management software layer according to the prior art. In GPRS,GMM V0.02 state machine provides two major states: GMM-Deregistered andGMM-Registered. In the design of access terminal 20, the software thatcontrols a microprocessor, which in turn controls the transceiver andI/O functions of access terminal 20, is divided into several or morelayers. Generally speaking each of these “layers” are related softwarecode, responsible for accepting inputs (some internally generated, someexternally), generating outputs (again, both internal and external) andprocessing received data to perform specific actions. “Layers” is a wayof organizing the code, to categorize functionality to increaseefficiency and economy of operation. These layers can be organized intoa state transition diagram which shows expected results for specificinputs. There concepts are well known by those skilled in the art ofsoftware design. In the prior art access terminal, there is a GMM layer301 and an RR layer 302.

[0024] A deregistered access terminal 20 will stay in a GMM-Deregisteredstate 302 in which access terminal 20 will not perform any routing areaupdates and the network will never page access terminal 20. A registeredaccess terminal 20 will stay in GMM-Registered state 304, whereby it caninitiate call/session setup, routing area update and be paged by thenetwork. Transition between the two states are caused by events shown inFIG. 3. Implicit in all prior art systems is that spot beams alwaysexist, and are always illuminated.

[0025] Upon power-on, GMM Layer 301 transitions from state 306 to GMMDeregistered (GMM Dereg.) PLMN Search State 308. Generally, indiscussing FIG. 3, transitions from one state to another will bereferred to as a “path”. Transitions from a state are described with thefollowing nomenclature: Paths are given designations representing thestate of origin. For example, a first path, “path A” originating fromstate 310, will be referred to as “path 310A”.

[0026] When GMM Layer 301 is in GMM Dereg. PLMN Search State 308, accessterminal 20 is searching for PLMNs; generally, any BCCHs, but mostprobably an A-BCCH 9. At this point, access terminal 20 is notregistered with any gateway, and that is why, as discussed above, GMMLayer 804 is described as being “de-registered”. In a “deregistered”state, access terminal 20 has GPRS capability enabled, but no GMMcontext has been established. In this state of being “deregistered”access terminal 20 may establish a GMM context by starting the GPRSattach procedure.

[0027] Eventually, a PLMN is identified, and GMM Layer 804 transitionsto either GMM Dereg. Normal Service State 310, or GMM Dereg. LimitedService State 308, via paths 308A or 308D respectively. Otherwise, GMMDereg. PLMN Search State 308 is left when it has been concluded that nocell is available at the moment, and GMM Layer 301 transitions to GMMDereg. No Cell Available State 336, via path 308C.

[0028] GMM Dereg. Normal Service State 310 is defined as the state towait for operator initiated registration request. In GMR-1, registrationis automatic and therefore this state has no waiting period. GMM Layer804 transitions from GMM Dereg. Normal Service State 310, through path310A, to GMM Dereg. Attach Needed State 312.

[0029] In GMM Dereg. Attach Needed State 312, valid subscriber data isavailable and for some reason a GPRS attach must be performed as soon aspossible. GMM Dereg. Attach Needed State 312 is usually of no duration,but can last if the access class is blocked. An access class representsa “quality of service” indicator. That it, different access classes areestablished (perhaps as many as 15 or more) and users may be assigned toany one of them. The user's quality of service may depend on the accessclass to which it belongs.

[0030] While GMM Layer 301 is in GMM Dereg. Attach Needed State 312, GMMLayer 301 sends a message to RR Layer 303 to perform an “AttachRequest“procedure, and GMM Layer 301 transitions through path 312A toGMM Registered (GMM Reg.) Initiated State 316. GMM Reg. Initiated State316 is an “in-between” state—neither de-registered as in state 302, norregistered as in state 304.

[0031] In GMM Reg. Initiated State 316, a GPRS attach procedure has beenstarted and access terminal 20 is waiting a response from the network.There can be several outcomes to this request. First, if the attempt toattach is rejected, GMM Layer 301 transitions to GMM Dereg. Attemptingto Attach State 314 via path 316A. GMM Dereg. Attempting to Attach State314 represents the condition in which no GMM Layer 301 procedure will beinitiated except a GPRS Attach. The execution of further attachprocedures depends on the GPRS attach procedure counter. However, whileGMM Layer 301 is in GMM Dereg. Attempting to Attach State 314, there areseveral other possible transitions that might also occur.

[0032] GMM “registered” defines a set of states in which a GMM contexthas been established, i.e. the GPRS attach procedure has beensuccessfully performed. In these states, access terminal 20 may activatePDP contexts, send and receive user data and signaling information, andmay reply to a page request. Furthermore, cell and routing area updatingare performed.

[0033] GMM Registered Normal Service State 318 is the state in whichuser data and signaling information may be sent and received. In GMMRegistered Update Needed State 320, access terminal 20 has to perform arouting area updating procedure, but its access class is not allowed inthe cell. The procedure will be initiated as soon as access is granted(this might be due to a cell-reselection or due to change of the barredaccess class of the current cell). No GMM procedure except routing areaupdating shall be initiated by access terminal 20 in GMM RegisteredUpdate Needed State 320. Additionally, while in GMM Registered UpdateNeeded State 320, no user data and no signaling information shall besent.

[0034] After transitioning to GMM Reg. Update Needed State 320, GMMLayer 804 causes a Routing Area Update (RAU) request to be issued, andthis places GMM Layer 804 in GMM Routing Area Update Initiated State322. Note that similarly to GNM Registered Initiated State 316, GMMRouting Area Update Initiated State 322 is neither registered 304 norderegistered 302, but, “in-between.” GMM Routing Area Update InitiatedState 322 is the state in which a routing area update procedure has beenstated and access terminal 20 is awaiting a response from the network.

[0035] Following the request, access terminal 20 is involved incommunications with NGW 12, and enters GMM Reg. Attempting to UpdateState 324, via path 322A. GMM Reg. Attempting to Update State 324 may bedescribed as the condition in which a routing area updating procedurehas failed due to a missing response from the network. Similar to attachprocedure, access terminal 20 retries the procedure controlled by timersand a GMPRS attempt counter. No GMM procedure except routing areaupdating shall be initiated by access terminal 20 while in this state.No data shall be sent or received.

[0036] GMM layer 301 may leave GMM routing area update initiate state322 via path 322B, if the RAU is accepted or if the RAU counter is lessthan five (5), a failure case occurs and the current RAI equals thestored RAI. If those conditions are true, GMM Layer 804 proceeds, viapath 322B, to GMM Reg. Normal Service State 318.

[0037] GMM Layer 301 may leave GMM Reg. Normal Service state 310 forseveral reasons. First, if n/w initiates a detach received withreattach, GMM Layer 301 transitions to GMM Dereg. Attempting To AttachState 314 via path 318B. Second, if n/w initiates a detach receivedwithout reattach implicit detach, GMM Layer 301 will transition to GMMDereg. Normal Service State 310 via path 318C. And lastly, if accessterminal originates a detach request, GMM layer 301 will transition toGMM Dereg. Initiated State 326, via path 318D. Once at GMM Dereg.Initiated State 326, GMM layer 301 will transition to GMM Dereg.Normal/Service State 310 via path 326B if the detach request isaccepted.

SUMMARY OF THE INVENTION

[0038] The above described disadvantages are overcome and a number ofadvantages are realized by the present invention which relates to asystem and method to facilitate providing a new service by a new serviceprovider to existing user access terminal of an existing serviceprovider; wherein the existing gateway may trigger the providing ofthese new services by either a specific request by the user terminal orby the existence of specific information, including the user terminal'sestablishment cause, SP/HPLMN ID or even its GPS position.

[0039] It is therefore object of the invention to provide a system andmethod to facilitate providing a new service to new user access terminalof both established and new service providers.

[0040] It is a further object of the invention to provide a system andmethod to efficiently provide access for new user access terminal to newservices without requiring the new service provider to acquire its ownsatellite transmission resources.

[0041] It is therefore an object of the invention to provide a systemand method to automatically trigger the illumination of a dark beambased on specific values of information elements contained in a channelrequest message, transmitted by a user.

[0042] It is therefore an additional object of the invention to providea system and method to deactivate and de-illuminate an illuminated beambased on specific criteria.

[0043] It is therefore an additional object of the invention to providea system and method to provide a mechanism for enabling successfulillumination of a dark beam by a user, by way of an extended pause timerand an illumination retry timer.

[0044] It is therefore an additional object of the invention to providea system and method to provide an interface between an existing gatewayand a new gateway.

[0045] It is therefore an additional object of the invention to providea system and method to provide an additional mechanism, a cell baraccess flag, for use in the illumination of a dark beam by a user.

[0046] These and other objects of the invention are provided by a methodfor operating a software layer in a user's access terminal in asatellite based telecommunications systems, comprising the steps ofentering a deregistered state from a power-off state, initiating anattach request procedure from an access terminal to an existing network,identifying a PLMN of a first broadcast channel, camping on the firstbroadcast channel, establishing deregistered service with a firstnetwork through use of the first broadcast channel, and entering aregistered illuminated state if a dark beam is illuminated and enteringa deregistered dark beam state if the dark beam is not illuminated, andengaging in telecommunication activities with a new network while in theregistered illuminated dark beam state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The novel features believed characteristic of the invention areset forth in the appended claims. The invention itself, however, as wellas other features and advantages thereof will be best understood byreference to the detailed description of the specific embodiments whichfollows, when read in conjunction with the accompanying drawings, inwhich:

[0048]FIG. 1 illustrates a block diagram of a satellite communicationsystem according to the prior art;

[0049]FIG. 2 illustrates a message flow diagram showing theestablishment of a communications channel between an access terminal andthe network according to the prior art;

[0050]FIG. 3 illustrates a state transition diagram for a GSM/GPRSmobility management software layer according to the prior art;

[0051]FIG. 4 illustrates a signal flow diagram showing the interactionbetween GMPRS mobility management software layer and radio resourcesoftware layer of an access terminal in accordance with an embodiment ofthe invention;

[0052]FIG. 5 illustrates a simplified state transition diagram for aGMPRS mobility management software layer according to an embodiment ofthe invention; and

[0053]FIG. 6 illustrates a detailed state transition diagram for a GMPRSmobility management software layer according to an embodiment of theinvention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0054] The various features of the preferred embodiment will now bedescribed with reference to the figures, in which like parts areidentified with the same reference characters.

[0055] The following detailed description of the preferred embodiment isrelated to two co-pending applications: “DARK BEAM OPERATION SCENARIO”,A. Noerpel, et al., Ser. No. ______; and “A. MOBILITY MANAGEMENT-RADIORESOURCE LAYER INTERFACE SYSTEM AND METHOD FOR HANDLING DARK BEAMSCENARIOS,” A Noerpel, et al., Ser. No. ______, the entire contents ofboth being expressly incorporated herein by reference.

[0056]FIG. 4 illustrates a signal flow diagram showing the interactionbetween GMPRS mobility management software layer and radio resourcesoftware layer of an access terminal in accordance with an embodiment ofthe invention. FIG. 4 shows generally how the two software layers, radioresource software layer (RR layer) 802 and GMPRS mobility managementlayer (GMM layer) 804 have been designed into access terminal 20.Generally, RR layer 802 receives or monitors all available channels,measuring signal strength on any channels showing activity (i.e.,presence of a signal). Thus, RR layer 802 performs threshold analysisfor all BCCH signals that are present (shown as step (1)). When areceived signal's parameters exceed established power criteria, RR layer802 passes the included system information to GMM layer 804 (shown asstep (2)), in the form of a list of PLMN IDs. GMM layer 804 then makesdecisions regarding beam illumination status (shown as step (3)), andprovides instructions to RR layer 802 (shown as step (4)) to camp on thecorrect BCCH (T-BCCH 11 (dark beam scenario) or A-BCCH 9).

[0057] Access terminal 20 provides users with several features that aretransparent to the user; that is, these are features that are a directresult of the design of RR layer 802 and GMM layer 804. These featureswill be briefly discussed, then the design of the two layers will bediscussed in greater detail.

[0058] RR layer 802 and GMM layer 804 provide users with the followingfeatures:

[0059] 1. Prioritization of Accessible Spot Beams (RR function).

[0060] A dark beam may have no accessibility for packet users due tovarious reasons. This is indicated by the combination of Cell Bar AccessFlag SIE 40 and Cell Bar Extension Flag SIE 42 transmitted in thecorresponding A-BCCH 9. Access terminal 20 should not camp on anon-accessible A-BCCH 9 unless there is no accessible A-BCCH 9available. Therefore, access terminal 20 must check Cell Bar Access FlagSIE 40 before doing anything else.

[0061] 2. Routing Area Update (RAU) Procedure (GMM function).

[0062] A routing area update (RAU) procedure is used to periodicallyinform the network that access terminal 20 is still “alive”, i.e., stillfunctioning in the area, and desirous of communicating in the network.If access terminal 20 does not inform the network it is interested, thenetwork will never page access terminal 20 when downlink data becomesavailable. Additionally, whenever access terminal 20 changes from onerouting area to another, due to user mobility, a RAU procedure is usedto inform the network about it its new location so that the networkknows where to page access terminal 20 the next time data is availablefor it. When access terminal 20 is in a dark beam, it should not performa RAU procedure at the expiry of RAU timer or a change of routing area.

[0063] 3. Registration Issue (GMM function).

[0064] In a dark beam, access terminal 20, after power on, shouldautomatically initiate an attach procedure as a preliminary step inattempting to illuminate the dark beam. An attach procedure is apreliminary step that registers an access terminal 20 with a network. Asa result, the user does not have to manually register himself beforeinitiating a service request (i.e., the method described in relatedapplication, Ser. No. ______, entitled ” DARK BEAM OPERATIONSCENARIO.”).

[0065] 4. Change of Beam Illumination Status (Combination of GMM and RRfunction).

[0066] If a dark beam becomes illuminated, all de-registered accessterminals 20 shall initiate an Attach Procedure to EGW 8 to registerthemselves. All registered access terminals 20 whose RAU timers havebeen expired or whose routing area identity (RAI) has been changed shallperform a RAU Procedure to update their status on the network. An RAI isutilized for paging purposes. Paging occurs when EGW 8 wishes tocommunicate with access terminal 20, so it verifies the location ofaccess terminal 20 with a paging process. The RAI is an identifiercreated and used by access terminal 20 to inform EGW 8 of its location.This is done whenever access terminal 20 enters a new spot beam (asdiscussed above) or when its RAU timer expires.

[0067] If an illuminated beam becomes dark, access terminal 20 shallcamp on an A-BCCH 9 of EGW 8. The change of selected network shall nottrigger access terminal 20 to initiate an attach procedure or RAUprocedure to the new network.

[0068]FIG. 5 illustrates a simplified state transition diagram for aGMPRS mobility management software layer according to an embodiment ofthe invention. In GMR-1, two more states have been added:GMM-Deregistered-Dark-Beam and GMM-Registered-Dark-Beam. The mostsignificant new state is GMM-Registered-Dark-Beam in which the accessterminal's 20 behavior is similar to GMM-Deregistered but it will neverupdate its routing area. In general, access terminal 20 GMM layer 804will utilize the standard GMPRS protocol stack with necessary updates inorder to accommodate a beam darkening situation. When a darkened beambecomes illuminated, GMM layer 804 will follow standard procedures thathave previously been used. These include the aforementioned proceduresof Attach/Detach, Routing Area Update (RAU), Periodical LocationRegistration. In a dark beam, access terminal 20 will not perform any ofthe operations mentioned above that tell the network where accessterminal 20 is. These are not performed because there is no requirementto perform downlink data transfer in dark beam, thereby savingfrequency/subband resources, even though the triggering condition isalready met. The trigger for Periodic Location Registration is timerexpiry or access terminal 20 moving from one beam to another. As aresult, GMM layer 804 sub-states have been created to describe whatoccurs in GMM layer 804 during a beam darkening event, as shown in FIGS.5 and 6. Although FIG. 6 will be discussed in detail below, during theensuing discussion of FIG. 5, reference will be made to the severalstates of FIG. 6 that correlate to that states of FIG. 5. FIG. 5 is, asmentioned above, a simplified version of FIG. 6.

[0069] Upon power-up, in step 902, access terminal 20 enters GMMDe-registered state 904. The terms “de-registered” and “registered”refer to the state of access terminal 20 in relation to acquiringservice from NGW 12: IF NGW 12 has knowledge of access terminal 20, thenaccess terminal 20 is “registered” with NGW 12, and can acquire service.If NGW 12 does not have knowledge of access terminal 20, then accessterminal 20 is in a state of being “de-registered”. The process ofregistration will only occur if a beam is illuminated when accessterminal 20 enters spot beam 10 (as discussed below), or becomesilluminated while waiting for the illuminating event while in spot beam10. Stricter definitions of “registered and deregistered” are given inreference to the discussion of FIG. 6.

[0070] Regardless of beam illumination status, access terminal 20 entersGMM Dereg-Light-Beam sub-state 906 (in reference to FIG. 6, all thestates of deregistered state 904 of FIG. 6 are contained inGMM-Dereg-Light-Beam state 906, except for State 1034; State 1034 isequivalent to GMM-Dereg-Dark-Beam state 908 of FIG. 5). By doing so, anAttach Request Procedure (i.e. a channel request) is automaticallyinitiated to the selected network. This is caused by access terminal 20transmitting Establishment Cause IE 44 on RACH 19, using Channel RequestMessage 13, with Attach/RAU Request ECV 45. The selected network in thisinstance is that network which access terminal 20 desires the newservice from, i.e., NGW 12. If the beam is illuminated triggered byAttach Request message sent from the access terminal 20, then the attachrequest is sent to NGW 12. The successful attach leads GMM layer 804 totransition to GMM-Reg-Light-Beam sub-state 912 (which is part of GMMRegistered state 910) in via path 906B.

[0071] If the Attach Request does not result in beam illumination due tolack of radio resource, access terminal 20 GMM layer 804 transitions toGMM-Dereg-Dark-Beam sub-state 908, in via path 906C, and performs idlemode access terminal 20 activities. If, however, the beam is illuminateddue to the triggering of the Attach Request message, access terminal 20is redirected to T-BCCH 11. This will trigger GMM layer 804 inGMM-Dereg-Light-Beam sub-state 906 to initiate another Attach RequestProcedure to NGW 12. A successful Attach Request Procedure will lead GMMlayer 804 to transition to GMM-Reg-Light-Beam sub-state 912 via path906B, as discussed above (“path” 906B actually corresponds to state 1014of FIG. 10; this is an “in-between” state, where access terminal 20 isneither registered, nor deregistered).

[0072] If while in GMM-Dereg-Dark-Beam sub-state 908 the beam isilluminated due to other user's activity, GMM layer 804 will transitionback to GMM-Dereg-Light-Beam sub-state 906 via path 908A and an AttachRequest Procedure is automatically initiated. A successful AttachRequest Procedure will lead GMM layer 804 to transition to GMMRegistered State 910 and GMM-Reg-Light-Beam sub-state 912 via path 906B,as discussed above.

[0073] While in GMM-Reg-Light-Beam sub-state 912, various activities canbe performed, including packet data profile (PDP) context activation(establishing packet date profile), RAU (routing area update), ServiceRequest (wherein access terminal 20 asks for data transfer service) andAnswering-to-Paging (in case the network has data to deliver to accessterminal 20 the network will first page access terminal 20, which shouldthen answer the paging). These are all shown as performed via path 912A.If access terminal 20 is in idle mode, it will perform idle modeactivities as described above.

[0074] However, at some certain point, the illuminated beam will becomedark. The beam darkening event will trigger GMM layer 804 to transitionfrom GMM-Reg-Light-Beam sub-state 912 to GMM-Reg-Dark-Beam sub-state 914via path 912B (in reference to FIG. 10, four states of FIG. 10 correlateto GMM-Reg-Dark-Beam state 914: States 1026, 1028, 1030 and 1032; thebalance correlate to GMM-Reg-Light-Beam state 912 of FIG. 9). If GMMlayer 804 of access terminal 20 is occupying GMM-Reg-Dark-Beam sub-state914, and a beam illumination event occurs, GMM layer 804 transitions toGMM-Reg-Light-Beam sub-state 912 via path 914A. An RAU Procedure will beinitiated if either access terminal 20 periodic RAU timer has expired orRAI has been changed since the last time attached request procedure orRAU has been performed.

[0075] Finally, while in GMM-Reg-Light-Beam sub-state 912, accessterminal 20 may decide to, or be forced to “detach” itself from the newservices provided by NGW 12. This could occur as a result of an explicitdetach request, an implicit detach request, an RAU procedure failure, orRAU resulting in a finding of an “indeterminate” (or invalid) position.Regardless of the exact reason, when access terminal 20 leaves GMMregistered state 910 (GMM-Reg-Light-Beam sub-state 912) it does so viapath 912C, and enters GMM deregistered state 904. As a result, accessterminal 20 is no longer registered with NGW 12, and entersGMM-Dereg-Light-Beam sub-state 906.

[0076]FIG. 6 illustrates a detailed state transition diagram for a GMPRSmobility management software layer according to an embodiment of theinvention. FIG. 6 explains in greater detail the operations of FIG. 5.Upon poweron, GMM Layer 804 transitions from state 902 to GMMDeregistered (GMM Dereg.) PLMN Search State 1008. Generally, indiscussing FIG. 6, transitions from one state to another will bereferred to as a “path”. Transitions from a state are described with thefollowing nomenclature: Paths are given designations representing thestate of origin. For example, a first path, “path A” originating fromstate 1010, will be referred to as “path 1010A”.

[0077] When GMM Layer 804 is in GMM Dereg. PLMN Search State 1008,access terminal 20 is searching for PLMNs; generally, any BCCHs, butmost probably an A-BCCH 9. At this point, access terminal 20 is notregistered with any gateway, and that is why, as discussed above inreference to FIG. 9, GMM Layer 804 is described as being“de-registered”. In a “deregistered” state, access terminal 20 has GPRScapability enabled, but no GMM context has been established. In thisstate of being “deregistered” access terminal 20 may establish a GMMcontext by starting the GPRS attach procedure. It is while in PLMNSearch State 1008 that access terminal 20 exercises the protocol methodsdescribed in related application Ser. No. ______. entitled “DARK BEAMOPERATION SCENARIO.”

[0078] Eventually, a PLMN is identified, and GMM Layer 804 transitionsto either GMM Dereg. Normal Service State 1010, or GMM Dereg. LimitedService State 1038, via paths 1008A or 1008B respectively. Otherwise,GMM Dereg. PLMN Search State 1008 is left when it has been concludedthat no cell is available at the moment, and GMM Layer 804 transitionsto GMM Dereg. No Cell Available State 1036, via path 1008C.

[0079] GMM Dereg. Normal Service State 1010 is defined as the state towait for operator initiated registration request. In GMR-1, registrationis automatic and therefore this state has no waiting period. GMM Layer804 transitions from GMM Dereg. Normal Service State 1010, through path1010A, to GMM Dereg. Attach Needed State 1012.

[0080] In GMM Dereg. Attach Needed State 1012, valid subscriber data isavailable and for some reason a GPRS attach must be performed as soon aspossible. GMM Dereg. Attach Needed State 1012 is usually of no duration,but can last if the access class is blocked. An access class representsa “quality of service” indicator. That it, different access classes areestablished (perhaps as many as 15 or more) and users may be assigned toany one of them. The user's quality of service may depend on the accessclass to which it belongs. If a dark beam indication is received GMMLayer 804 will transition to GMM Dereg. Normal Service Dark Beam State1034 via path 1012C.

[0081] GMM Dereg. Normal Service Dark Beam State 1034 represents thesituation in which access terminal 20 is attempting an attach or adetach procedure which could not be completed due to dark beamindication. GMM Dereg. Normal Service Dark Beam State 1034 ends whenaccess terminal 20 receives a trigger from upper layers (i.e., from GMMlayer 804 to RR layer 802), or a light beam indication (i.e., a darkbeam is illuminated) and GMM Layer 804 transitions to GMM Dereg. NormalService State 1010 through GMM Dereg. PLMN Search State 1008 via paths1034A and 1008A.

[0082] While GMM Layer 804 is in GMM Dereg. Attach Needed State 1012,GMM Layer 804 sends a message to RR Layer 802 to perform an “AttachRequest” procedure, and GMM Layer 804 transitions through path 1012A toGMM Registered (GMM Reg.) Initiated State 1014. GMM Reg. Initiated State1014 is an “in-between” state—neither de-registered as in state 804, norregistered as in state 810.

[0083] In GMM Reg. Initiated state 1014, a GPRS attach procedure hasbeen started and access terminal 20 is waiting a response from thenetwork. If a dark beam indication is received before a peer levelresponse from the network indicating lack of resources, GMM Layer 804will transition to GMM Dereg. Normal Service Dark Beam State 1034 viapath 1014C. If a status indication is received from RR Layer 802, with acause indicating “Switch to new BCCH”, GMM Layer 804 will transition toGNM Dereg. PLMN Search State 1008, via path 1014C (to GMM Dereg. NormalService Dark Beam State 1034 and then through path 1034A to GMM Dereg.PLMN Search State 1008). RAU Timer (T3310) will be stopped.

[0084] In GMM Reg. Initiated State 1014, access terminal 20 (morespecifically, RR Layer 802) waits for a network to respond. There can beseveral outcomes to this request. First, if the attempt to attach isrejected, GMM Layer 804 transitions to GMM Dereg. Attempting to AttachState 1016 via path 1014B. GMM Dereg. Attempting to Attach State 1016represents the condition in which no GMM Layer 804 procedure will beinitiated except a GPRS Attach. The execution of further attachprocedures depends on the GPRS attach procedure counter. However, whileGMM Layer 804 is in GMM Dereg. Attempting to Attach State 1016, thereare several other possible transitions that might also occur.

[0085] Second, if a beam darkening event occurs, or an ImmediateAssignment Reject Message 15 is received GMM Layer 805 will transitionto GMM Dereg. Normal Service Dark Beam State 1034. There are severalerror cases that the Immediate Assignment Reject Message (response fromthe network) can contain that will cause this last transition: the firstis Non Availability of Satellite Resource RCV 37, (resource notavailable); second is non-availability of services and third is“position too old.”

[0086] Third, if a status indication is received (i.e., ImmediateAssignment Reject Message 15) from RR Layer 802 with Switch to NewT-BCCH reject cause value, GMM Layer 804 will transition to GMM Dereg.PLMN Search State 1008, via path 1016A (to GMM Dereg. Normal ServiceDark Beam State 1034) and then via path 1034A to GMM Dereg. PLMN SearchState 1008.

[0087] Fourth, if the routing area update (RAU) timer expires, GMM Layer804 will transition to GMM Reg. Update Needed State 1020, via path1016B, to GMM Dereg. Attached Needed State 1012 (where the Attach isattempted), to GMM Dereg. GMM Registered Initiated State 1014 via path1012A, and then to GMM Reg. Normal Service State 1018 via path 1014A,and finally to GMM Reg. Update Needed State 1020 (where the RAU processcan begin), via path 1018A.

[0088] GMM “registered” defines a set of states in which a GMM contexthas been established, i.e. the GPRS attach procedure has beensuccessfully performed. In these states, access terminal 20 may activatePDP contexts, send and receive user data and signaling information, andmay reply to a page request. Furthermore, cell and routing area updatingare performed.

[0089] GMM Registered Normal Service State 1018 is the state in whichuser data and signaling information may be sent and received. Onreceiving a dark beam indication, GMM Layer 804 will transition to GMMRegistered Normal Service Dark Beam State 1032.

[0090] In GMM Registered Update Needed State 1020, access terminal 20has to perform a routing area updating procedure, but its access classis not allowed in the cell. The procedure will be initiated as soon asaccess is granted (this might be due to a cell-reselection or due tochange of the barred access class of the current cell). No GMM procedureexcept routing area updating shall be initiated by access terminal 20 inState 1020. Additionally, while in State 1020, no user data and nosignaling information shall be sent. On receiving a dark beam indicationGMM Layer 804 will transition to GMM Registered Normal Service Dark BeamRouting Area Update State 1026 via path 1020B.

[0091] After transitioning to GMM Reg. Update Needed State 1020, GMMLayer 804 causes a Routing Area Update (RAU) request to be issued, andthis places GMM Layer 804 in GMM Routing Area Update Initiated State1022. Note that similarly to GMM Registered Initiated State 1014, GMMRouting Area Update Initiated State 1022 is neither registered (904) norderegistered (910), but “in-between.” GMM Routing Area Update InitiatedState 1022 is the state in which a routing area update procedure hasbeen stated and access terminal 20 is awaiting a response from thenetwork. If a dark beam indication is received before a response fromthe network, access terminal 20 will transition to GMM Registered NormalService Dark Beam RAU State 1026 via path 1022B. Timer T3330 will bestopped, the attempt counter will not be incremented, and the GU Statuswill not be changed.

[0092] Following the request, access terminal 20 is involved incommunications with NGW 12, and enters GMM Reg. Attempting to UpdateState 1024, via path 1022A. GMM Reg. Attempting to Update State 1024 isdescribed by the condition in which a routing area updating procedurehas failed due to a missing response from the network. Similar to attachprocedure, access terminal 20 retries the procedure controlled by timersand a GMPRS attempt counter. No GMM procedure except routing areaupdating shall be initiated by access terminal 20 while in this state.No data shall be sent or received.

[0093] If the beams darkens at this time, then GMM Layer 804 transitionsfrom GMM Reg. Attempting to Update State 1024, to GMM Reg. NormalService Dark Beam RAU State 1026 via path 1024B. Else, if the beam staysilluminated, GMM Layer 804 will remain in GMM Reg. Attempting to UpdateState 1024, until another RAU update is needed, or the beam goes dark,or the user no longer desires new services from NGW 12.

[0094] GMM Reg. Normal Service Dark Beam State 1032 is the state inwhich the GMM Layer 804 shall enter (via path 1018B) upon receiving adark beam indication when in GMM Reg. Normal Service State 1018. No userdata and signaling shall be sent by access terminal 20 when in GMM Reg.Normal Service Dark Beam State 1032. GMM Layer 804 will remain in thisGMM Reg. Normal Service Dark Beam State 1032 until a trigger is receivedto send user data, the RAI timer (T3312) expires or a light beamindication is received. On receiving a light beam indication GMM Layer804 will transition to GMM Reg. Normal Service State 1018 via path1032B. If a trigger is received to send user data GMM Layer 804 willtransition to GMM Reg. Illumination Initiated State 1030. On expiry ofthe RAI Timer (T3312), GMM Layer 804 will transition to GMM Reg. NormalService Dark Beam RAU State 1026.

[0095] GMM Reg. Illumination Initiated State 1030 is the state GMM Layer804 shall enter when it receives a trigger to send user data while inGMM Reg. Normal Service Dark Beam State 1032. User data is buffered inthis state until a light beam or dark beam indication is received or RAItimer (T3312) expires. On receiving a light beam indication or a statusindication (Immediate Assignment Reject Message 15) from the lowerlayers with a reject cause indicating Switch to new T-BCCH RCV 35, GMMLayer 804 will transition to GMM Reg. Normal Service State 1018, viapath 1030B, and send the buffered data. If a dark beam indication isreceived, access terminal will discard buffered data and return to GMMReg. Normal Service Dark Beam State 1032 via path 1030C. On expiry ofRAI Timer (T3312) GMM Layer 804 will transition to GMM Reg. IlluminationInitiated RAU State 1028 via path 1030A.

[0096] GMM Reg. Normal Service Dark Beam RAU State 1026 is the state GMMLayer 804 shall enter when it receives a dark beam event whileattempting to perform a routing area update (from GMM Routing AreaUpdate Initiated State 1022) or the RAI Timer (T3312) expires while inGMM Reg. Normal Service Dark Beam State 1032, via path 1032C. GMM Layer804 will remain in GMM Reg. Normal Service Dark Beam RAU State 1026until it receives a light beam indication or a trigger to send userdata. On receiving a light beam indication GMM Layer 804 will transitionto GMM Reg. Update Needed State 1020 via path 1026B. If a trigger isreceived to send user data while in GMM Reg. Normal Service Dark BeamRAU State 1026, GMM Layer 804 will transition to GMM Reg. IlluminationInitiated RAU State 1028, via path 1026A.

[0097] GMM Reg. Illumination Initiated RAU State 1028 is the state GMMLayer 804 shall enter when it receives a trigger to send user data inwhile in GMM Reg. Normal Service Dark Beam RAU State 1026 (via path1026A) or RAI Timer (T3312) expires while waiting for a beam indicationwhile in GMM Reg. Illumination Initiated State 1030, via path 1030A.User data is buffered while in GMM Reg. Illumination Initiated RAU State1028 until a light beam or dark beam indication is received. Onreceiving a light beam indication GMM Layer 804 will transition to GMMReg. Update Needed State 1020, via path 1028A, and perform a routingarea update. If a dark beam indication is received GMM Layer 804 willreturn to GMM Reg. Normal service Dark Beam RAU State 1026, via path1028B.

[0098] GMM Dereg. Invalid Position State 1040 is a state that is enteredfrom: GMM Routing Area Update Initiated State 1022 via path 1022C; GMMReg. Normal Service State 1018 vic path 1018D; and GMM RegisteredInitiated State 1014 via path 1014D for several reasons. While in GMMDereg. Invalid Position State 1040, access terminal will, if timer T3213expires, perform a periodic routing update. The following paragraphsexplain the relative importance of this state, and the reasons why GMMLayer 804 enters this state.

[0099] Multiple Gateway Stations may provide service within a spot beam.However, the coverage of a spot beam is large, and the Gateway Stationsmay only be allowed to provide coverage in a portion of the beam. Also,different Gateway Stations might provide service into differentgeographic regions within a spot beam 10. Gateway Stations inform accessterminals 20 about position based service limitation via reject causesin response to Channel Request messages.

[0100] If access terminal 20 is at a location from which service mightbe obtained but not from the location area identifier (LAI) that wasselected by access terminal 20, a Channel Request message can berejected with the reject cause “Invalid position for the Selected LAI.”The selected LAI is no longer available. Access terminal 20 shall selectany other LAI that is still available. If access terminal 20 receivesthis cause upon access of the final “Available” LAI, it shall treat thiscase in the same manner as for “Invalid Position.”

[0101] If access terminal 20 is at a location from which service is notavailable from any Gateway Station, the Channel Request message shall berejected with the reject cause “Invalid Position” or “Invalid Positionfor the access terminal's Service Provider.” Access terminal 20 shallconsider all LAIs for this GMR-1 system to be not available and ceasePLMN and LAI selection for the GMR-1 system. Access terminal 20 mayremain in the Service Level (Normal Service or Limited Service) that wasin effect prior to the Channel Request message.

[0102] There are number of situations in which the registration statusof access terminal 20 cannot be determined, and access to the system isblocked in any case. The inability to obtain Normal Service is due toone or more of the following factors:

[0103] An “Invalid Position” or “Invalid Position for the AccessTerminal's Service Provider” response to a Channel Request; and

[0104] A “Position Too Old” response to a Channel Request for an LR.

[0105] Under any of these conditions, access terminal's 20 registrationstatus is indeterminate, and access terminal 20 may provide onlyPosition-Restricted Service(s). Position-Restricted Service differs fromLimited Service in that access terminal 20 will not attemptnon-emergency calls for the latter. If access terminal 20 is inPosition-Restricted Service, and the user attempts a call, accessterminal 20 will attempt location registration and then follow with theservice request, if it is successful. Other aspects of thePosition-Restricted and Limited Services, such as non-responsiveness topages and high-penetration alerts, are the same.

[0106] Spot beam selection is influenced by the “Invalid Position forthe Selected Spot Beam” error cause in the Immediate Assignment Rejectmessage.

[0107] If access terminal's 20 services “Invalid Position for theSelected Spot Beam” and the selection indication (SI) bit, (whichindicates whether a BCCH is allowed to camp on) is:

[0108] not set, no BCCH from this spot beam 10 (on the same satellite 6)shall be allowed for camp-on; or

[0109] set, no BCCH from this satellite shall be allowed for camp-on.

[0110] This error cause shall always have a BCCH Carrier associated withit. Access terminal 20 shall synchronize to the associated BCCH carrier.If the reselection indication (RI) bit (indicating whether beamreselection is needed) is not set, the access terminal 20 shall evaluatethe spot beam for suitability for camping on. If the RI bit is set, theaccess terminal 20 shall conduct a spot beam selection among this BCCHand the BCCHs of its BCCH_NEIGHBOR_LIST and identify suitable spot beams10. After identifying new suitable spot beams, if any, access terminal20 shall identify new suitable BCCHs, if any.

[0111] During a spot beam selection procedure that is executed incompliance with this clause, access terminal 20 might only identify newsuitable BCCHs that are also on the Forbidden BCCH List (see laterclauses). In this circumstance, access terminal 20 may identify a spotbeam 10 as suitable even if it is more than a preset amount of decibelsweaker than the strongest spot beam 10, provided that it is thestrongest spot beam 10 not already disallowed for camp-on and that itexceeds the minimum BCCH power threshold.

[0112] The present invention has been described with reference tocertain exemplary embodiments thereof. However, it will be readilyapparent to those skilled in the art that it is possible to embody theinvention in specific forms other than those described of the exemplaryembodiments described above. This may be done without departing from thespirit of the invention. The exemplary embodiments are merelyillustrative and should not be considered restrictive in any way. Thescope of the invention is defined by the appended claims and theirequivalents, rather than by the preceding description.

What is claimed is:
 1. A method for operating a software layer in auser's access terminal in a satellite based telecommunications systems,comprising the steps of: entering a deregistered state from a power-offstate; initiating an attach request procedure from an access terminal toan existing network; identifying a PLMN of a first broadcast channel,camping on the first broadcast channel and establishing deregisteredservice with a first network through use of the first broadcast channel;entering a registered illuminated state if a dark beam is illuminated,and entering a deregistered dark beam state if the dark beam is notilluminated; and engaging in telecommunication activities with a newnetwork while in the registered illuminated dark beam state.
 2. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 1, furthercomprising: entering a registered dark beam state from a registeredilluminated state; and leaving the registered dark beam state to enterthe registered illuminated state.
 3. The method for operating a softwarelayer in a user's access terminal in a satellite basedtelecommunications systems according to claim 1, further comprising:leaving the deregistered dark beam state for an deregistered illuminatedstate.
 4. The method for operating a software layer in a user's accessterminal in a satellite based telecommunications systems according toclaim 1, wherein the step of establishing a deregistered service with afirst network comprises: entering a deregistered illuminated normalservice state from a deregistered illuminated PLMN search state based ona first set of conditions; and entering a deregistered limited servicestate from a deregistered illuminated PLMN search state based on asecond set of conditions.
 5. The method for operating a software layerin a user's access terminal in a satellite based telecommunicationssystems according to claim 4 wherein the first set of conditionscomprises: a cell being found in an illuminated beam.
 6. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 4 wherein the secondset of conditions comprises: all PLMNs found by the access terminal areon a forbidden list, or that registration of a mobility managementsoftware layer has failed due to lack of available resources.
 7. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 1, whereinthe step of entering a registered illuminated dark beam state if a darkbeam is illuminated comprises: entering a deregistered illuminatedattach needed state from the deregistered illuminated normal servicestate based on a third set of conditions; entering an illuminated GMMregistered initiated state from the deregistered illuminated attachneeded state based on a fourth set of conditions; and entering into aregistered illuminated normal service state from the GMM registeredilluminated initiated state based on a fifth set of conditions.
 8. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 7, whereinthe third set of conditions comprises: an attach request is initiated toa second network from the access terminal in a first network.
 9. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 7, whereinthe fourth set of conditions comprises: the attach request istransmitted from the access terminal in the first network to the secondnetwork.
 10. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 7, wherein the fifth set of conditions comprises: theattach request is accepted by the second network.
 11. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 1, wherein the stepof entering a dark beam deregistered state if the dark beam is notilluminated comprises: entering into the deregistered dark beam normalservice state from the deregistered illuminated attach needed state,based on a sixth set of conditions.
 12. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 11, wherein: the sixth setof conditions is a condition selected from the group consisting of abeam darkening event, an immediate assignment reject message indicatingthat the new service is not available, an immediate assignment rejectmessage indicating that the resource is not available and an immediateassignment reject message indicating that the reported position of theaccess terminal is too old.
 13. The method for operating a softwarelayer in a user's access terminal in a satellite basedtelecommunications systems according to claim 2, wherein the step ofentering a registered dark beam state from a registered illuminatedstate upon the existence of one or more of a first group of conditionscomprises: entering a registered dark beam normal service state from aregistered illuminated normal service state to based on a seventh set ofconditions.
 14. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 13, wherein the seventh set of conditions comprises:the illuminated beam is darkened.
 15. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 2, wherein the step ofleaving the registered dark beam state to enter the registeredilluminated state comprises: entering a registered illuminated normalservice state from a registered dark beam normal service state based onan eighth set of conditions.
 16. The method for operating a softwarelayer in a user's access terminal in a satellite basedtelecommunications systems according to claim 15, wherein the eighth setof conditions comprises: the dark beam is illuminated.
 17. The methodfor operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 3, whereinthe step of leaving the deregistered dark beam state for a deregisteredilluminated state comprises: entering a deregistered illuminated PLMNsearch state from a deregistered dark beam normal service state based ona ninth set of conditions.
 18. The method for operating a software layerin a user's access terminal in a satellite based telecommunicationssystems according to claim 17, wherein the ninth set of conditionscomprises: the dark beam is illuminated.
 19. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 1, further comprising:initiating a position update procedure while in a registered illuminatedstate.
 20. The method for operating a software layer in a user's accessterminal in a satellite based telecommunications systems according toclaim 19, wherein: the registered illuminated state is either aregistered illuminated normal service state or a registered illuminatedlimited service state.
 21. The method for operating a software layer ina user's access terminal in a satellite based telecommunications systemsaccording to claim 19, wherein: the initiated position update procedurewhile in a registered illuminated state is performed successfully. 22.The method for operating a software layer in a user's access terminal ina satellite based telecommunications systems according to claim 19,wherein: the initiated position update procedure while in a registeredilluminated state is not performed successfully.
 23. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 21, wherein the stepof performing the initiated position update procedure while in aregistered illuminated state successfully comprises: entering aregistered illuminated update needed state from the registeredilluminated normal service state based on a tenth set of conditions;entering a registered illuminated GMM routing area update initiatedstate from the registered illuminated update needed state based on aeleventh set of conditions; and entering the registered illuminatednormal service state from the registered illuminated GMM routing areaupdate initiated state based on an twelfth set of conditions.
 24. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 23,wherein the tenth set of conditions comprises: a routing area updatetimer has expired or a change in routing area has occurred to the accessterminal.
 25. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 23, wherein the eleventh set of conditions comprises:a routing area update request is transmitted.
 26. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 23, wherein thetwelfth set of conditions comprises: the routing area update request isaccepted, or a routing are update attempt counter is less than anattempt counter number, a failure case occurs and a current routing areaindicator equals a stored routing area indicator.
 27. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 26, wherein theattempt counter number is
 5. 28. The method for operating a softwarelayer in a user's access terminal in a satellite basedtelecommunications systems according to claim 21, wherein the step ofperforming the initiated position update procedure while in a registeredilluminated state is not performed successfully comprises: entering aregistered illuminated update needed state from the registeredilluminated normal service state based on a tenth set of conditions;entering a registered illuminated GMM routing area update initiatedstate from the registered illuminated update needed state based on aneleventh set of conditions; entering a registered illuminated attemptingto update state from the registered illuminated GMM routing area updateinitiated state; entering the registered illuminated update needed statefrom the registered illuminated attempting to update state based on athirteenth set of conditions; and repeating these steps until therouting area update request is accepted, or a routing are update attemptcounter is less than an attempt counter number, a failure case occursand a current routing area indicator equals a stored routing areaindicator.
 29. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 28, wherein the thirteenth set of conditionscomprises a T3311 timer expires or a T3302 timer expires.
 30. The methodfor operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 28,further comprising: entering a registered dark beam normal servicerouting area update state from the registered illuminated GMM routingarea update initiated state, the registered illuminated attempting toupdate state or the registered illuminated update needed state based ona beam darkening event.
 31. The method for operating a software layer ina user's access terminal in a satellite based telecommunications systemsaccording to claim 1, further comprising entering a registered dark beamnormal service state from the registered illuminated normal servicestate; and entering a registered dark beam normal service routing areaupdate state from the registered dark beam normal service state.
 32. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 31,wherein the step of entering a registered dark beam routing area updatestate from the registered dark beam state comprises: entering aregistered dark beam illuminated initiated state from the registereddark beam normal service state based on a fourteenth set of conditions;entering a registered dark beam illumination initiated routing areaupdated state from the registered dark beam illumination initiated statebased on a fifteenth set of conditions; and entering a registered darkbeam normal service dark beam routing area update state based on asixteenth set of conditions.
 33. The method for operating a softwarelayer in a user's access terminal in a satellite basedtelecommunications systems according to claim 32, wherein the fourteenthset of conditions comprises: a user request.
 34. The method foroperating a software layer in a user's access terminal in a satellitebased telecommunications systems according to claim 32, wherein thefifteenth set of conditions comprises: a T3312 timer expiration or abeam reselection.
 35. The method for operating a software layer in auser's access terminal in a satellite based telecommunications systemsaccording to claim 32, wherein the sixteenth set of conditionscomprises: an illumination failure.
 36. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 32, further comprising:entering the registered dark beam normal service state from theregistered dark beam illumination initiated state based on anseventeenth set of conditions; and entering the registered illuminatednormal service state based on a eighteenth set of conditions.
 37. Themethod for operating a software layer in a user's access terminal in asatellite based telecommunications systems according to claim 36,wherein the seventeenth set of conditions comprises: an illuminationfailure.
 38. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 36 wherein the eighteenth set of conditionscomprises: a beam illumination or a rejection to a new broadcast controlchannel.
 39. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 32 further comprising: entering an registeredilluminated update needed state from the registered dark beamillumination initiated routing area update state based on a nineteenthset of conditions.
 40. The method for operating a software layer in auser's access terminal in a satellite based telecommunications systemsaccording to claim 39 wherein the nineteenth set of conditionscomprises: a beam illumination or a rejection to a new broadcast controlchannel.
 41. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 31 further comprising: entering a registered darkbeam normal service state from the registered dark beam normal servicerouting area update state based on a twentieth set of conditions. 42.The method for operating a software layer in a user's access terminal ina satellite based telecommunications systems according to claim 41wherein the twentieth set of conditions comprises: expiration of a T3312timer or a beam reselection event.
 43. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 41 further comprising:entering the registered dark beam illumination initiated routing areaupdate state from the registered dark beam normal service routing areaupdate state based on a twenty-first set of conditions; and entering theregistered illuminated update needed state from the registered dark beamnormal service routing area update state based on a twenty-second set ofconditions.
 44. The method for operating a software layer in a user'saccess terminal in a satellite based telecommunications systemsaccording to claim 43 wherein the twenty-first set of conditionscomprises: a user request.
 45. The method for operating a software layerin a user's access terminal in a satellite based telecommunicationssystems according to claim 43 wherein the twenty-second set ofconditions comprises: a beam illumination.
 46. The method for operatinga software layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 1, further comprising:entering a deregistered state from a plurality of registered statesbased on a twenty-third set of conditions.
 47. The method for operatinga software layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 46 wherein thederegistered state comprises: a GMM deregistered illuminated invalidposition state.
 48. The method for operating a software layer in auser's access terminal in a satellite based telecommunications systemsaccording to claim 46 wherein the twenty-third set of conditionscomprises: an invalid position of the access terminal, an invalidposition for the access terminal's SP, or, an invalid position forselected location area identities and no additional location areaidentities are available.
 49. The method for operating a software layerin a user's access terminal in a satellite based telecommunicationssystems according to claim 46 wherein the registered states comprises:the registered illuminated normal service state and the illuminated GMMrouting area update initiated state.
 50. The method for operating asoftware layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 1, further comprising:entering a deregistered state from the GMM registered initiated statebased on a twenty-fourth set of conditions.
 51. The method for operatinga software layer in a user's access terminal in a satellite basedtelecommunications systems according to claim 50, wherein thederegistered state comprises: a GMM deregistered illuminated invalidposition state.
 52. The method for operating a software layer in auser's access terminal in a satellite based telecommunications systemsaccording to claim 50, wherein the twenty-fourth set of conditionscomprises: an invalid position of the access terminal, an invalidposition for the access terminal's SP, or, an invalid position forselected location area identities and no additional location areaidentities are available.